"We are in a very important period. We have been negotiating for quite a long time. [ ] After the coming of President Rouhani we see the first change of tone, change of atmosphere. And now we see some substance in their proposals," said Amano at the Washington-based Wilson Center.

He added: "It is important that additional protocol will be implemented, timely information about the nuclear facilities of Iran will be provided, and some other issues with possible military dimensions will be clarified."

His comments come as the five permanent members of the Security Council plus Germany -- dubbed as the P5+1 group -- prepares to resume nuclear negotiations with Iran on November 7-8 in Geneva, Switzerland. The IAEA will meet with Iranian officials shortly thereafter in Tehran on November 11.

Still, even as Iran and the IAEA takes steps forward, Amano cautioned against expecting rapid progress.

"Not everything can come overnight, and Iran proposed a step by step approach, and this proposal contains some substance. We are now working on that."

Syrian nuclear facility 'under safeguard'

Amano said that Syria’s miniature neutron source reactor is currently under IAEA safeguard, but that the agency hasn’t been able to inspect the site recently due to "obvious reasons".

The research reactor is located just outside of Damascus.

Amano added that the nuclear watchdog hoped to verify related facilities, saying, "There are three. But these facilities are not under safeguard. We need negotiation with them to have access to them, and we have not yet had access to these facilities. We don't know how these facilities are for now."

Commenting on the facility destroyed in an Israeli airstrike in Deir az Zour in 2007, Amano said that the IAEA concluded, "It is very likely that it was a nuclear reactor."